Differential Scanning Calorimetric Results Research Articles

Mechanism of improving the mechanical and barrier properties of poly(lactide)/poly(butylene adipate‐co‐terephthalate) blends

AbstractPoly(lactide)/poly(butylene adipate‐co‐terephthalate) (PLA/PBAT) blends containing different amounts of polyethylene wax (PEW) were fabricated via melt‐blending, and the effects of PEW on the interfacial morphological evolution and properties of the PLA/PBAT blends were investigated. Scanning electron microscopy (SEM) micrographs show that the compatibility between PLA and PBAT is obviously improved by addition of low contents of PEW. Differential scanning calorimeter (DSC) results indicate that PEW can simultaneously enhance the crystallization ability of PLA and PBAT. Rheological behavior of the blends indicates that PEW has a significant plasticizing effect and can promote the mobility of polymer chains in the blends. More importantly, it is revealed that PEW can effectively improve the mechanical and barrier properties of the blends. Even with a PEW content of only 1 wt%, the elongation at break and notched impact strength of the blend reach 344.1% and 12.55 kJ/m2, respectively, which are 54% and 140% higher than the blend without PEW. Meanwhile, the water vapor transmission rate (WVTR) and oxygen transmission rate (OTR) of the films containing 1 wt% PEW are decreased from 87.34 to 67.40 g m−2·24 h−1 and from 118.26 to 80.94 cm3 m−2·24 h−1, respectively, which are 22.8% and 31.5% lower than those of the PLA/PBAT film.

Reactive Ti/Ni multilayer composites produced via accumulative roll-bonding (ARB): post-annealing treatment

ABSTRACT Ti/Ni multilayers, produced through the accumulative-roll bonding (ARB) process, serve as reactive multilayer, capturing energy to optimize manufacturing processes and contribute to TiNi (shape memory alloy) production. This research specifically examines the impact of the number of layers on microstructural and thermal properties after activation through heating. Energy-dispersive spectroscopy (EDS), field emission scanning electronmicroscopy (FESEM), and differential scanning calorimeter (DSC) were employed to analyse samples subjected to various ARB cycles. The findings indicate that in low-cycle ARB processing, the interdiffusion of Ni and Ti under normal conditions initiates the production of a very thin layer of TiNi at 800 °C, requiring extended holding times for increased thickness. Conversely, the formation of intermetallic compounds, particularly TiNi, and diffusion in high-cycle ARB-processed composites are accelerated. According to the DSC results, complete activation and phase transformation, accompanied by the release of energy (43–50 kJ/mol), occur at approximately 500–525°C without the need for any holding time. Consequently, for achieving a uniform TiNi phase, heat treatment of high-cycle ARB-processed composites up to 800°C – a temperature surpassing the activation temperature – without any holding time can be effectively employed.

Mechanical, Rheological, and Heat Seal Properties of 1‐Octene Grafted Low Density Polyethylene Films

AbstractHeat seal and mechanical properties of 1‐octene grafted low density polyethylene films containing various concentrations of Dicumyl peroxide as the initiator and 1‐octene grafting agent is investigated through using experimental measurements. The results of differential scanning calorimeter (DSC) measurements revealed that the melting temperature shifts to higher values and the peak of the DSC curve becomes wider with the increase of 1‐octene concentrations. Thermogravimetric analysis (TGA) revealed a higher thermal stability up to 20 °C for 1‐octene grafted PE compared with neat LDPE alloy. The results of stress–strain measurements revealed that the 1‐octene grafted PE alloys has higher tensile strength in comparison with neat PE alloy and samples containing only DCP initiator. The results of heat seal analysis indicated that both DCP initiator and 1‐octene tended to offer a moderate increase peel strength of PE alloy. DMTA measurements for various grafted PE alloys show a higher damping factor in comparison with neat LDPE alloy. Rheological measurements indicated a higher storage modulus up to 25% and higher complex viscosity for grafted PE samples containing 1‐octene comonomer.

Effect of e-waste nanofillers on the mechanical, thermal, and wear properties of epoxy-blend sisal woven fiber-reinforced composites

Abstract Lignocellulosic biomass extracted from plants that contain rich amounts of cellulose, hemicellulose, and lignin content can replace synthetic fibers in many engineering applications and is biodegradable. However, e-waste is rapidly evolving into one of the most serious environmental issues in the world owing to the presence of several toxic compounds that can contaminate the environment and pose a threat to human health. Printed circuit boards (PCBs) are one of the major components available in e-waste. In this research work, waste PCB (WPCB) powder is mixed in suitable proportions of 5%, 10%, 15%, and 20% with a lignocellulosic sisal woven fabric fiber mat, and blended with epoxy resin using the vacuum-assisted hand lay-up method. To determine the effect of particle size on the fabricated composites, mechanical, thermal, water absorption, surface roughness, and wear tests were conducted. It was found that the composition that contains 15% nanofiller composites gave better results in mechanical testing than the composition that contains 10% microfiller composites. Pin-on disc wear test and differential scanning calorimetric thermal test results show that 10% microfiller composites show better outcome results than 15% nanofiller composites. Testing values indicate that lignocellulosic sisal fiber composites with WPCB nano- and microfillers can be substituted for many engineering applications instead of being disposed of in landfills.

One-Step Preparation of Fiber-Based Chlorzoxazone Solid Dispersion by Centrifugal Spinning.

An amorphous fiber-based solid dispersion of chlorzoxazone was prepared for the first time by employing centrifugal spinning, using polyvinylpyrrolidone as the fiber-forming polymer. After optimization of the spinning parameters, the obtained fibers were characterized using a set of analytical techniques, both in a solid- and solution-state. Morphological characterization revealed a slightly aligned, defect-free fibrous structure with an average fiber diameter of d = 3.07 ± 1.32 μm. The differential scanning calorimetric results indicated a crystalline-to-amorphous transition of the active substance during the centrifugal spinning process, while gas chromatographic determinations revealed a residual ethanol content of 0.42 ± 0.04%. UV spectroscopy indicated the incorporation of chlorzoxazone in the fibrous structures, with an average active substance content of 15.91 ± 0.36 w/w%. During small-volume dissolution studies, the prepared fiber mats presented immediate disintegration upon contact with the dissolution media, followed by rapid dissolution of the active substance, with 84.8% dissolved at 1 min and 93.7% at 3 min, outperforming the micronized, pure chlorzoxazone. The obtained results indicate that centrifugal spinning is a low-cost, high-yield, viable alternative to the currently used methods to prepare fiber-based amorphous solid dispersions of poorly soluble drugs. The prepared chlorzoxazone-loaded microfibers could be used as a buccal dosage form for the systematic delivery of chlorzoxazone and could potentially lead to a rapid onset of action and longer efficacy of the muscle relaxant drug.

Development of artificial leak-free phase change material (PCM) aggregates using emulsion technique, cementless binder, and cold-bonded pelletization

The present study developed new leak-free artificial PCM aggregates using an emulsion technique, cementless binder, and cold-bonded pelletization (hereafter, PCM-surfactant-aggregate) and significantly increased the PCM quantity in aggregates without PCM leakage, which was demonstrated from differential scanning calorimetric (DSC) and thermogravimetry (TG) results. The PCM-water-emulsion was produced by using a non-ionic surfactant, Pluronic P123, and used as mixing water to produce cementless artificial aggregates using Ca(OH)2-Na2CO3-activated fly ash and cold-bonded pelletization. The produced artificial PCM-surfactant-aggregates showed no material separation during preparation and no visual PCM leakage on the surface and were lightweight aggregates in terms of compressive strength (ASTM C330). In the concrete testing results, the 28-day compressive strength was 18.1 MPa when all fine and coarse aggregates were replaced with artificial PCM-surfactant-aggregates and the thermal conductivity decreased with increasing aggregate content. The testing on the heated concrete specimens having PCM-surfactant-aggregates indicated no PCM leakage, no dimensional change, and no strength reduction due to the PCM phase transition from solid to liquid. Overall, the concrete containing PCM-surfactant-aggregates showed an increase in the lowest temperature and a decrease in the highest temperature in the temperature profile of the indoor space in the dynamic heat flow test.

Preparation and characterization of phase change capsules containing waste cooking oil for asphalt binder thermoregulation

The green utilization of waste is of great significance to the sustainable development of human society. In this work, a new kind of capsule with the phase change heat storage function was prepared using waxy components extracted from waste cooking oil (WCO) as core material for the thermoregulation of asphalt binder. The differences in waxy components before and after hydrolysis treatment were studied including functional groups, phase transition temperature, and phase transition enthalpy. Meanwhile, the surface morphology, thermodynamic properties, and mechanical properties of the phase change capsules (PCCs) were also characterized comprehensively. Additionally, the effect of PCCs on asphalt thermoregulation was also examined in the laboratory. The results indicate that the waxy components after hydrolysis treatment are more suitable for asphalt binder thermoregulation in terms of the phase transition temperature, phase transition enthalpy, and thermal stability. According to the results of differential scanning calorimeter and thermogravimetric experiments, it can be calculated that the ratio of wall material and core material in PCCs is about 1:1, which endows the capsule with excellent heat storage properties (125 J/g), mechanical properties (>13 N), and thermal stability (>190 ℃). With the help of the temperature sensor, it is found that PCCs can delay the change rate of asphalt temperature with the environment by undergoing a phase transition to mitigate the damage of asphalt pavement in extremely hot climates. However, the performance of PCCs in asphalt mixtures still needs to be further explored. Overall, the findings of this research can further promote the green utilization of WCO and the functionalization of construction and building materials.

Fabrication and characterization of microencapsulated dimethyl adipate phase change material with melamine-formaldehyde shell for cold thermal energy storage in coating

Abstract Microencapsulated phase change material (MPCM) was synthesized by using the in-situ polymerization technique. Dimethyl adipate (DMA) and melamine-formaldehyde were used as core and shell material for polymerization respectively. Sodium laureate sulphate (SLS) is used as a surfactant. The thermal properties were characterized by using a differential scanning calorimeter (DSC) and thermogravimetry analysis (TGA). Fourier transform infrared spectroscopy (FT-IR) was used to confirm the chemical structure. The morphology of microcapsules was studied by using, scanning electron microscopy. DSC result of MPCM has been observed to melt at 10.09 °C with melting latent enthalpy 88 J/g and crystallizes at 4.69 °C with crystallization latent heat 89.50 J/g. TGA analysis confirms increases in the thermal stability of MPCM. The decorative coating was prepared with 0, 5, 10, 15, and 20 % MPCM loading, and the prepared paint was tested for pencil hardness, gloss, and stain resistances. The thermal energy transfer rate was used to measure how much time coated panel took to reach the equilibrium temperature of 25 °C. Coating with 20 % MPCM loading revealed good thermal storage capacity but other general coating properties deteriorate.

Reaction mechanism study and modeling of thermal runaway inside a high nickel-based lithium-ion battery through component combination analysis

To diagnose and elucidate thermal runaway accompanying gas evolution of a lithium-ion battery, it is essential to understand the thermal side reactions that lead to thermal runaway inside a lithium-ion battery. It is very useful to make a reliable model that represents these reactions to analyze thermal runaway processes in order to secure battery safety and overcome high costs of large-scale experiments. This study proposes the reaction mechanism and the reaction model through the design of experiments with the combination of battery components such as a cathode, an anode, an electrolyte, and a separator. To develop the reaction mechanism, the peak temperature and calorific value of each reaction are obtained by using a differential scanning calorimeter. The change of mass and produced gas from each reaction are identified by using an online thermogravimetry-mass spectrometer. Based on these measurements, the reaction model is developed by estimating kinetic parameters obtained from the Kissinger analysis. The reaction model exhibits root-mean-square-error of 1.91 mW, 21.79 mW, and 4.53 mW in the electrolyte, the cathode and the anode, respectively, as compared to differential scanning calorimeter results, confirming its high fidelity. The proposed model illustrates the variation of volume fractions of each phase inside a lithium-ion battery to simulate electrochemical performance degradation during thermal runaway stage. The change in internal pressure is also evaluated by using the change in mass and volume of each phase. Based on the mechanism and model derived from this study, it is possible to pinpoint the electrochemical performance degradation and heat generation characteristics during thermal runaway.

Insights into the modification of physicochemical properties and digestibility of pea starch gels with barley β-glucan.

The influences of barley β-glucan (BBG) on the physicochemical properties and in vitro digestibility of pea starch were investigated. BBG was found to decrease pasting viscosity in a concentration dependent manner and inhibited the aggregation of pea starch. After the presence of BBG, the gelatinization enthalpy of pea starch was decreased (from 7.83±0.03 to 5.55±0.22J/g), whereas the gelatinization temperature was enhanced (from 62.64±0.01 to 64.52±0.14°C) according to the differential scanning calorimeter results. In addition, BBG inhibited the swelling of pea starch and amylose leaching. When amylose leached out from pea starch to form a BBG-amylose barrier, starch gelatinization was inhibited. The starch gels exhibited weak gels and shear thinning behaviors by rheological tests results. The interaction between BBG and amylose led to lower viscoelasticity and texture parameters in pea starch gels. The structure analysis results unveiled that the force between BBG and amylose was mainly hydrogen bonds. Pea starch hydrolysis was inhibited when BBG was present in the system, which was connected with the restricted starch gelatinization. These results obtained in the study would supply insights into incorporating BBG into various food systems.

Heating De-fluorination derived radicals promoted interfacial grafting and enhanced Kevlar/Bismaleimide composites

Lack of stable, active reacting centers of fiber with bismaleimide (BMI) resin severely limited interfacial properties of composites. In this article, we found defluorination derived radicals under high temperature was able to participate into BMI resin curing reaction. X-ray Photoelectron Spectroscopy (XPS), In-situ Fourier Transform Infrared Spectroscopy (FTIR) and Thermogravimetric Analysis-Fourier Transform Infrared Spectroscopy-Gas Chromatography/Mass (TGA-GC/MS) Spectrometry hyphenated testing results of model molecules revealed decomposition process of fluorinated layer, and in-situ Electron Paramagnetic Resonance (EPR) captured alkyl radicals from defluorination. According to Differential Scanning Calorimeter results, above radicals were able to promote curing of BMI resin via radical coupling, which meant definite covalent combination between fluorinated aramid fiber and BMI matrix. Therefore, composite interfacial shear strength (IFSS) and interlaminar shear strength (ILSS) simultaneously enhanced by 41.93% and 31.44% at maximum, respectively. Consequently, flexural properties of laminates also increased where flexural strength and flexural modulus respectively improved by 26.29% and 35.24%.

Nano additives-enhanced PEG /AlN composites with high cycle stability to improve thermal and heat storage properties

The low thermal conductivity and easy leakage of phase change materials are the shortcomings that hinder their further application for thermal energy storage. It is crucial how to properly match skeleton materials and phases to improve heat transfer in order to solve the above problem. Here, we systematically investigate the effects of nano additives on the phase change and thermal properties of bionic hierarchical porous aluminum nitride-polyethylene glycol (PEG/AlN) composites. Alumina (Al2O3) nanoparticles were found to have the largest enhancement effect for the thermal conductivity of PEG (84% for 4 wt% addition) compared to silica, titanium dioxide, and boron nitride. For these additives, the thermal conductivity and stability of the nano additives-enhanced PEG increase with the increase of their mass fraction. After 100 heating/cooling cycles, the thermal response curve shows that the Al2O3-enhanced PEG can maintain the phase transition behavior, and the measured phase transition temperature agrees well with the differential scanning calorimeter results. The thermal conductivity of the PEG/AlN enhanced with 4 wt% Al2O3 is 20.41 W/m·K, and the melting point and phase change enthalpy are 55.93 °C and 81.05 J/g. In addition to the great improvement in thermal response, the heat storage rate also increases by 36.10%.

Preparation and characterization of modified activated carbon-based shape stabilized eutectic phase change materials for gypsum composites application

Modified SAT-urea eutectic salts (EPCM) as the phase-change materials were prepared using modifiers such as disodium hydrogen phosphate dodecahydrate (DHPD) and carboxymethyl cellulose (CMC). The support material, hydrophilic modified activated carbon (MAC), was prepared using OP-10 as a hydrophilic modifier. The vacuum impregnation method was used to fabricate the MAC-based shape-stabilized eutectic phase-change materials (SSEPCM). The gypsum-based building materials with thermal storage capacity were obtained by compositing surface-treated SSEPCM and gypsum. The surface contact angle, surface functional group, phase transition temperature, latent heat, phase composition, and microstructure of the SSEPCM were examined using the static contact angle meter, Fourier infrared spectrometer, in-situ infrared spectrometer, differential scanning calorimeter, X-ray diffractometer, and scanning electron microscope. The adsorption capacity of MAC increased first and then decreased with the increase of OP-10 content in the modified solution. When the OP-10 content was 0.3 wt%, the contact angle between the surface of MAC and water reduced to 0°, and the mass fraction of EPCM relative to MAC was 93.1 wt%. The results showed that the OP-10 had a good hydrophilic modification effect on the granular activated carbon. The X-ray diffractometer and differential scanning calorimeter results of SSEPCM indicated that there was no chemical reaction between EPCM and MAC, the phase transition temperature was 32.11 °C, and the latent heat was 103 J/g. The latent heat loss rate of SSEPCM was 5.8 % after 100 thermal cycles, and the number of –OH did not decrease during the heating process of SSEPCM, which showed that SSEPCM had good thermal stability. The flexural and compressive strength values of the SSEPCM/gypsum composites were 2.50 MPa and 7.36 MPa, respectively, when 45 wt% SSEPCM was incorporated into the gypsum matrix, which was sufficient for practical applications. The introduction of SSEPCM could slowly reduce the thermal conductivity and significantly improved the thermal inertia of the composites.

Measurement method for T-h properties of phase change material

ABSTRACT In this study, a simple and inexpensive T-h property measurement method was proposed for measuring the temperature and specific enthalpy of a flat plate phase change material (PCM) by cooling and heating it under adiabatic conditions on one side and constant heat flux from the opposite side. Experiments were conducted by choosing the temperature on the adiabatic side, which is less affected by the heat transfer surface, as the representative temperature of the PCM and reducing the thickness of the sample installed in the equipment with low heat flux. The experimental results demonstrated that the T-h properties can be measured under quasi-steady conditions of cooling and heating. In addition, the PCM, which was measured as the hysteresis occurring between cooling and heating using differential scanning calorimeter (DSC) measurements, was measured using this system. The results showed that the T-h characteristics of cooling and heating were almost identical, except for the supercooling phenomenon, and that it is possible to measure supercooling and its cancellation phenomenon, which is difficult to measure in the DSC results. Furthermore, it was confirmed that this equipment had sufficient measurement accuracy; accordingly, it was possible to measure the thermal properties of the PCM relatively accurately.

The Eff ect of Pregelatinized Starch on the Properties of Poly (Vinyl Alcohol) Film for the Water-Soluble Laundry Bag

The goal of this study was to develop pregelatinized starch (P-St) and polyvinyl alcohol (PVOH) fi lms as water-soluble laundry plastic bags to avoid having contact with COVID-19 infected clothes by extrusion method. The effects of pregelatinized starch (P-St) content on the properties of polyvinyl alcohol (PVOH) fi lms were examined. PVOH and P-St blend were compounded by twin- screw extruder with various P-St content of 0, 10, 20, 30, and 40% by weight with fi xed glycerol content of 20 phr. The blend fi lms were produced by blown fi lm extrusion. The chemical structure, thermal properties, water-solubility, mechanical properties, and the cross-sections morphological properties of PVOH/G/P-St were characterized. As a result, the formation of intermolecular interactions between PVOH, glycerol and P-St was confi rmed by FTIR. Moreover, the addition of P-St on PVOH could reduce the thermal stability due to the content of P-St with amylose, a substance of amorphous structure, affecting the chains fl exibility of PVOH/G/P-St. From the differential scanning calorimeter result, the glass transition temperature was increased with the increment of P-St content because the chains entanglement between PVOH and P-St had affected the reduction in crystallinity and led to the decrement of the melting temperature. Furthermore, the water solubility would strongly be dependent on the percentage of the gelatinized starch (%GS). The solubility decreased as the percentage of the GS increased. In addition, PVOH with 20% of P-St fi lm possessed the highest value in tensile strength and modulus, and the particles of P-St have a good distribution in PVOH/G indicating to stronger interaction of P-St and PVOH/G.

Synthesis of alkynyl phosphite ligands and its application in the preparation of high stability one‐component heat‐curable silicone rubber

AbstractHydrosilylation reaction is one of the main ways to obtain silicone rubber vulcanized products in the industry. However, it still remains a challenge for the currently used catalyst to obtain one‐component silicone rubbers with Karstedt's catalyst. In this work, we synthesize a series of phosphite ligands by transesterification, which are further used in combination with Karstedt's catalyst to prepare one‐component silicone rubber. The structure of the ligand is characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance and the vulcanization properties of silicone rubber are investigated by rotorless vulcanizer, differential scanning calorimeter (DSC) and rotational viscometer. It is found that the complex catalysts have low catalytic activity at ambient temperature when the ratio of P:Pt exceeds 1:1. The viscosity growth results show that the prepared silicone rubber has a storage time of more than 30 days at 25°C, and can be completely cured within 10 min at 150°C. The DSC results indicate that one of the prepared catalysts exhibited relatively strong catalytic activity only above 110.7°C. Moreover, the prepared complex catalyst can effectively avoid the production of colloidal platinum and prolong the storage stability of the catalyst.

Effect of Chemical Treatment of Sugar Palm Fibre on Rheological and Thermal Properties of the PLA Composites Filament for FDM 3D Printing.

The thermal and rheological properties of bio-composite filament materials are crucial characteristics in the development of a bio-composite Fused Deposition Modeling (FDM) filament since the printing mechanism of FDM strongly depends on the heating and extrusion process. The effect of chemical treatment on the thermal and rheological properties was investigated to develop composite filaments for FDM using natural fibres such as sugar palm fibre (SPF). SPF underwent alkaline and silane treatment processes before being reinforced with PLA for improving adhesion and removing impurities. Thermogravimetric Analysis (TGA), Differential Scanning Calorimetric (DSC), and Melt Flow Index (MFI) analyses were conducted to identify the differences in thermal properties. Meanwhile, a rheological test was conducted to investigate the shear stress and its viscosity. The TGA test shows that the SPF/PLA composite treated with NaOH and silane showed good thermal stability at 789.5 °C with 0.4% final residue. The DSC results indicate that the melting temperature of all samples is slightly the same at 155 °C (in the range of 1 °C), showing that the treatment does not interfere with the melting temperature of the SPF/PLA composite. Thus, the untreated SPF/PLA composite showed the highest degradation temperature, which was 383.2 °C. The SPF/PLA composite treated with NaOH and silane demonstrated the highest melt flow index of 17.6 g/min. In conclusion, these findings offer a reference point for determining the filament extrusion and printability of SPF/PLA composite filaments.

In situ monitoring of epoxy resin curing process: Using glass transition as a bridge

Dielectric analysis (DEA) is an effective method for monitoring the curing process of epoxy resin (EP) in situ, but the influence of curing temperature on the measurement results limits the application of DEA in curing process monitoring with variable temperature. In this study, the theoretical basis of using the glass transition as a bridge and monitoring the curing degree by ionic conductivity was analyzed. DEA experiments and differential scanning calorimeter (DSC) experiments were carried out and the mathematical model of ionic conductivity, glass transition temperature, and curing degree of the EP established. The parameters in the model were only related to the composition of EP system in the model as verified for implementing curing-degree monitoring of the EP system cured at variable temperature. The FT-IR spectra measurement was carried out and the activation energy of curing reaction was calculated by results of DEA and DSC, which verified the reliability and scientificity of the method. The method of using glass transition as a bridge can monitor the curing degree in the curing process with variable temperature and extends DEA to the monitoring of this process under variable temperatures.

An investigation on demineralization induced modifications in the macromolecular structure and its influence on the thermal behavior of coking and non-coking coal

Eight coking and non-coking coals have been studied by Wide Angle X-ray Scattering (WAXS), Fourier Transform Infrared Spectroscopy (FTIR), and TG/DTG (Thermogravimetry/Derivative Thermogravimetry) – DSC (Differential Scanning Calorimeter). The FTIR study shows that the demineralization treatment significantly influences –OH, aliphatic (–CH3, –CH2), aromatic (C=O), and aromatic nucleus (C=C) functional groups of the raw coals. The structural parameters like interlayer spacing (d002), crystallite size (Lc), lateral size (La), aromaticity (fa)XRD, and rank (I26/I20) are determined from WAXS. The WAXS results of demineralized coal show that d002 (range 3.75–3.51 Å) decreases, but (fa)XRD (range 0.69–0.88) increases with the increase of elemental carbon percentage (Cdaf) and rank of coals. The combustion and kinetic parameters of these coals have been evaluated by TG/DTG – DSC analysis. The ignition temperature (Ti), DTG Tpeak, DSC Tpeak, and burnout temperature (Tb) vary in the range of 338–410 °C, 475–551 °C, 490–555 °C, and 579–641 °C, respectively for demineralized coals however variations of these parameters for raw coals are 345–361 °C, 462–621 °C, 467–631 °C, and 560–675 °C, respectively. The TG/DTG – DSC and FTIR results show that demineralization influences the thermal behaviors and functional groups vis-à-vis structural moieties of coals.

Bio-based poly(vinyl benzoxazine) derived from 3-hydroxycinnamic acid— An intrinsically green flame-retardant polymer free of both halogen and phosphorus

A novel bio-based benzoxazine monomer (VBOZ-7, 7-vinyl-3-phenyl-3,4-dihydro-2H-1,3-benzoxazine) bearing polymeriable vinyl and 1,3-benzoxazine functionalities was synthesized from 3-hydroxycinnamic acid through successive decarboxylation reaction and Mannich condensation.The styrene-like bifunctional monomer underwent radical polymerization to obtain soluble P(VBOZ-7) which still remainining polymeriable benzoxazien pendent groups. The reactive P(VBOZ-7) possessed excellent solubility just like polystyrene, and also showed excellent thermal stability under 220 °C verified by differential scanning calorimeter (DSC) results. When the linear P(VBOZ-7) was heated over 240 °C, the remaining benzoxazines polymerized rapidly to form crosslinked structure. Thermogravimetric analysis (TGA) results showed that both linear and crosslinked P(VBOZ-7) possessed high char-formability at 800 °C. Cone calorimeter test (Cone test) proved that in situ crosslinking reaction strikingly improved the flame-retardancy of P(VBOZ-7). The total heat release of the crosslinked P(VBOZ-7) was only 6.7 MJ/m2, far below the value of polystyrene (109.4 MJ/m2). Undoubtedly, the P(VBOZ-7) consisting of C, H, O, N atoms is an intrinsically green flame-retardant polymer with excellent solution processibility.